A model for the disposition of centrally and peripherally produced norepinephrine has been used to design experiments to separately quantify the central and peripheral production rates of norepinephrine in vivo. Analytical methods required for the execution of these studies have been established in this laboratory. These include the measurement of norepinephrine, normetanephrine, 3-methoxy-4-hydroxy phenylglycol and vanilmandelic acid by gas chromatography-mass spectrometry.